Electrode comparison

ER308L vs ER309L

ER308L matches 304 base metal; ER309L is over-alloyed so it survives dilution when TIG or MIG welding stainless to carbon steel.

ER308L vs ER309L at a glance

	ER308L	ER309L
AWS specification	AWS A5.9/A5.9M	AWS A5.9/A5.9M
Process	TIG (GTAW) / MIG (GMAW)	TIG (GTAW) / MIG (GMAW)
Form	Solid wire / rod	Solid wire / rod
Tensile strength (min)	75 ksi	75 ksi
Yield strength (min)	45 ksi	45 ksi
Elongation (min)	35%	30%
Impact toughness	Not required; austenitic deposits stay tough to cryogenic temperatures	Not required by the specification
Polarity	DCEP (GMAW), DCEN (GTAW)	DCEP (GMAW), DCEN (GTAW)
Positions	Flat, Horizontal, Vertical, Overhead	Flat, Horizontal, Vertical, Overhead
Penetration	Medium	Medium
Deposition rate	Medium to high depending on process	Medium to high depending on process
Coating / core	None — bare wire or rod	None — bare wire or rod
Slag	None; a light oxide film should be brushed or pickled off	None; light oxide film to be cleaned
Shielding gas	100% argon for TIG; tri-mix 90% He / 7.5% Ar / 2.5% CO2 for spray MIG	100% argon for TIG; tri-mix or 98/2 for MIG
Storage	Keep clean and dry. Contamination, not moisture, is the main enemy for bare stainless filler.	Clean, dry, isolated from carbon steel contamination.
Primary use	Sanitary tube and pipe welding for food, dairy and pharma	Stainless-to-carbon-steel transition joints

Which should you use?

Same logic as the covered electrode versions, applied to bare wire. ER308L is a 19Cr-10Ni filler that matches Type 304 and is the standard rod for sanitary and process piping. ER309L runs richer at 23Cr-12Ni so that dilution from a carbon steel member still leaves a sound, ferrite-bearing austenitic deposit. On a stainless-to-stainless joint ER308L is correct and cheaper; on anything involving carbon steel, ER309L is the one that will not crack.

Choose ER308L when

Welding 304 or 304L to itself
Sanitary tube, food and pharma piping
Standard stainless TIG and MIG fabrication

Choose ER309L when

Stainless to carbon steel transition joints
First layer of a stainless overlay
Unknown base metals in repair work

Amperage compared

Diameter	ER308L	ER309L
0.030 in (0.8 mm) MIG	50–150 A	50–150 A
0.035 in (0.9 mm) MIG	70–180 A	70–180 A
0.045 in (1.2 mm) MIG	100–250 A	100–250 A
1/16 in (1.6 mm) TIG	40–90 A	40–90 A
3/32 in (2.4 mm) TIG	70–130 A	70–130 A
1/8 in (3.2 mm) TIG	100–180 A	100–180 A

Ranges are typical starting points. Diameters listed for only one electrode are shown as — for the other.

ER308L vs ER309L — common questions

Which filler for welding 304 to mild steel?

ER309L. ER308L diluted by carbon steel turns martensitic and cracks; ER309L starts over-alloyed so the diluted deposit stays austenitic with enough ferrite to resist hot cracking.

Do they use the same shielding gas?

Yes — pure argon for TIG, and a helium tri-mix or a low-CO2 argon mix for MIG. The gas choice follows the process, not the alloy.

Is ER309L a good general-purpose stainless rod?

It welds most austenitic grades soundly and is a popular repair filler, but it costs more than the matching rod and offers no advantage on a matching joint.

Full specifications

ER308L

AWS A5.9/A5.9M

ER308L is the bare wire and TIG rod for 304 and 304L stainless — the same low-carbon 19Cr-10Ni chemistry as E308L, without a flux coating.

ER309L